1. Field of the Invention
The present invention relates to an improved mobile communication apparatus for use on a mobile vehicle such as, for example, a delivery truck.
2. Description of the Prior Art
It is frequently desirable to communicate with a driver of a vehicle while the driver is on the road. For example, it may be necessary to inform the driver of a recent delivery or pick-up change, or it may be desirable to know the driver's current position so as to up-date delivery schedules. While two-way radios, for example, citizen band radios, permit communication with a driver, they are limited in transmission range which typically inhibits direct communication between the driver and a central office. Further, as the driver may not know his current position, either in terms of standard grid coordinates or other identifying means, the driver's current position cannot be accurately updated.
To overcome the above problems, the assignee of the present application introduced a satellite communication system which generally comprises a mobile communication unit, known as the Sony 2-Wayfarer.TM. Mobile Communication Unit, a geosynchronous satellite, a communication center and tracking software contained within a processing device located at a user's operation center. This communication system enables messages transmitted from the user's operation center to be received at a mobile vehicle and further enables vehicle positioning data, driver initiated messages and externally sensed information to be transmitted from the vehicle to the user's operations center. As shown in FIG. 1, the mentioned satellite communication system 5 permits two-way communication between a driver in a vehicle 10 and a remote operation center 25 by way of a geosynchronous satellite 20 and a communication center 15. More specifically, operation center 25 may communicate with communication center 15 by way of telephone lines (not shown), or similar medium, and center 15 communicates with vehicle 10 by way of satellite 20.
FIG. 2 illustrates a mobile communication unit 45 according to the prior art, which may constitute the Sony 2-Wayfarer.TM. unit, and which generally comprises a Loran-C receiving antenna 50, a main processing unit 55, for example, in the form of a suitable micro-processor, a receiver/interface unit 60, a transmit/receive antenna 65 and an enhanced keyboard/display unit 70. Radio waves transmitted by Loran-C stations (not shown) are received by Loran-C antenna 50 and supplied to main processing unit 55 through a cable 51, which is preferably a coaxial cable. Upon receipt of a request signal from the operation center 25 (FIG. 1) such as a vehicle positioning request signal, as hereinafter described, the processing unit 55 is adapted to calculate the current vehicle position from the received Loran-C radio waves and to process the position information into a digital signal which is supplied to the transmit/receive antenna 65, whereupon the digital signal is amplified and suitably transmitted to the satellite 20 (FIG. 1). Processing unit 55 is further adapted to receive information from sensor devices (not shown) located on the vehicle, which may be used for monitoring various functions of the vehicle, for example, the engine temperature. Signals requesting such information, like the vehicle positioning request signals, are supplied from center 25, by way of communication center 15 and satellite 20, through the transmit/receive antenna 65 to receiver/interface unit 60, as hereinafter described, whereupon the request signal is forwarded to processing unit 55. Upon receipt of such a requested signal, unit 55 processes the received engine temperature or other sensor information into a digital signal which is suitably processed and supplied to transmit/receive antenna 65 for transmission to satellite 20 as previously described. The processed digital signal may include a portion having an unique address code for identifying the transmitting vehicle, as hereinafter described.
Transmit/receive antenna 65 is further adapted to receive from satellite 20 signals which may contain a vehicle identifying address code, and to supply the received signals to receiver/interface unit 60. Unit 60 determines if the address code contained within the received signal matches that associated with the respective vehicle and which may be stored in a non-volatile memory (not shown) contained within unit 60. If a match is detected, unit 60 processes the received signal and supplies the same to keyboard/display unit 70. Further, a plurality of group address codes in which each group address code identifies a unique group of vehicles, as hereinafter described, may be stored in a programmable memory (not shown) also contained within unit 60. Thus, a transmitted signal containing a group address code will be received, processed and supplied to keyboard/display unit 70 in each mobile communication unit 45 in which a match is detected between one of the stored address codes contained within the respective unit 60 and the group address code contained within the received signal. On the other hand, if a match is not detected, the received signal is not further processed. Thus, the transmitted signal is only processed by the receiver/interface unit 60 contained within the designated vehicle or vehicles, thereby providing reasonable security for the message sent from operation center 25 (FIG. 1).
The signals transmitted from communication center 15 to communication unit 45 by way of satellite 20 are typically formatted into packets of information as shown in FIG. 3A. As shown therein, each packet includes an 8 bit start flag at the leftmost position which may have the value of 01111110.sub.2, or 7E.sub.HEX. Adjacent to the start flag is a 16 bit address field which contains the address of a designated vehicle or a designated group of vehicles. Alternatively, the address field may address all vehicles by utilizing, for example, an address consisting of all one's. As shown in FIG. 3A, each packet of the signal further includes a 6-bit block sequence number, a 2-bit selector field, a data field for containing information data in 6-bit bytes up to a maximum of 762 bits, a 6-bit checksum field and an 8-bit end flag which may have the same value as the start flag. Insertions of zeros from the start of the address field to the end of the checksum field in each packet is performed in accordance with the high-level data link control (HDLC) standard so as to prevent "false flags" from occurring. In a sequence of packets, the end flag of one packet may be used as the start flag of the subsequent packet. Further, during idle periods, that is, when no information data are sent from communication center 15, vehicle 10 receives a steady stream of flags from communication center 15.
The signals transmitted from communication unit 45 to communication center 15 by way of satellite 20 are typically formatted into packets of information as shown in FIG. 3B. As shown therein, each packet includes an acquisition sequence which enables the communication center 15 to acquire the transmitted signal. A synchronization sequence follows the acquisition sequence and is utilized to enable the communication center 15 to become synchronized with the received signal. Following the synchronization sequence is a length field which indicates the length of the packet, a routing address field which provides routing information, a physical address field which contains the identifying address of the respective communication unit 45 transmitting the current signal, a format selector which indicates the format of the following block sequence number and the internal diad, a block sequence number which indicates a sequential number for each packet, an internal diad field which contains application layer information relating to the respective communication unit 45 and which may include hardware status, sensor status and position information, an application packet which also contains application layer information and which may include data or messages from the keyboard/display unit 70, a cyclic redundancy check (CRC) field which contains error detection information and a forward error correction (FEC) field which contains the flush bits of the error correction encoding. The number of bits in each of the above described portions or fields is indicated in FIG. 3B. As shown therein, the maximum number of data bits from the length field through the CRC field is 1024 bits.
The receiver/interface unit 60 may contain an intelligent interface processor (not shown) for enabling devices external to communication unit 45, for example, a refrigerator unit, to be monitored and controlled in a manner similar to that previously described. Keyboard/display unit 70 is adapted to receive and display the processed signal from unit 60 which allows the respective message to be read by the driver. For that purpose, the unit 70 is located in relatively close proximity to the driver. Associated with unit 70 is an audio or visual alarm (not shown) which is activated when a processed signal is received by unit 70, so as to alert the driver to the reception of a message. Unit 70 is further adapted to receive driver initiated messages, which are entered through a keyboard device. Such entered messages are supplied through unit 60 to processing unit 55, whereupon the messages are processed to form a digital signal supplied to antenna 65 for transmission to operation center 25 as previously described.
As previously mentioned and as shown in FIG. 1, geosynchronous satellite 20 receives digital signals transmitted from vehicle 10 and communication center 15 and, in turn, amplifies and relays the digital signals to communication center 15 and vehicle 10, respectively. By using geosynchronous satellite 20, two-way communication is effected between an operation center and a vehicle located over a relatively large predetermined area, for example, within the continental United States. Further, two geosynchronous satellites may be advantageously utilized, that is, one for receiving messages from vehicle 10 and for relaying the same to communication center 15 and one for receiving messages from communication center 15 and for relaying the same to vehicle 10.
Communication center 15 (FIG. 1) receives a transmitted signal from satellite 20 and identifies the designated user from the address code contained therein, whereupon the signal is routed to the designated user by way of telephone lines, or similar medium. In a similar manner, center 15 receives signals from a plurality of operation centers, such as operation center 25, and such signals are, in turn, transmitted to satellite 20.
Operation center 25 (FIG. 1) transmits signals to center 15 for transmission to a designated vehicle. These signals may request a vehicle's position, control a desired function or supply the driver with information as previously described. Further, center 25 receives signals from vehicle 10 by way of satellite 20 and center 15, and such signals are supplied to a central processing device (not shown) located in center 25. The received signals are processed by the central processing device, which includes tracking software, and may be displayed on a detailed map along with any messages or data which may have been transmitted.
Thus, while the 2-Wayfarer.TM. Communication Unit, when used with satellite 20, center 15 and a processing device containing tracking software, enables two-way communication between a vehicle and an operation center, it may give rise to a safety hazard if the driver seeks to read transmitted messages from the keyboard/display unit 70, or seeks to transmit messages by way of the keyboard thereof, while vehicle movement is possible.